Complications of Anaesthesia

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General anaesthesia (GA) and regional anaesthesia (RA) are the main types of anaesthesia.
Complications depend on the type of anaesthesia received.
Airway injuries\: lips, tongue, gum, dentition, glottic structures; sore throat common post-GA.
Bronchospasm/laryngospasm\: higher risk in hyper-responsive airways, can cause hypoxia.
Aspiration\: life-threatening, higher risk in non-fasted, pregnant, obese patients; may cause pneumonia.
Pulmonary complications\: pneumothorax, pulmonary oedema, hypoxia, pharyngeal obstruction, embolism.
Cardiovascular complications\: hypotension, arrhythmias, hypertension; manage by addressing underlying causes.
Genitourinary complications\: acute kidney injury (AKI) due to various causes; urinary retention in older patients.
Gastrointestinal complications\: post-operative nausea and vomiting (PONV), ileus; manage with antiemetics, address
reversible factors.
Neurological complications\: postoperative cognitive dysfunction (POCD) in older patients; peripheral nerve injuries due to
positioning.
cardiac events.
Hypothermia\: common in perioperative period, prevent with warming strategies; can cause infection, coagulopathy,
Regional anaesthesia complications\: post-dural puncture headache (PDPH), major neurological complications from
central neuraxial blocks, peripheral nerve injuries.
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Introduction

There are two main types of anaesthesia administered to patients to perform surgery\:
General anaesthesia (GA)
Regional anaesthesia (RA)
Complications of anaesthesia mostly depend on the type of anaesthesia the patient has received.
This article will focus on the complications of general anaesthesia, with a short section on the complications of regional
anaesthesia.

Respiratory system

Airway
Injury to lips, tongue, gum, dentition and other oral soft tissue structures can occur during airway instrumentation. In
patients with loose teeth, there is a risk of dislodgement and subsequent tooth aspiration.
Injury to structures of the glottisGlottic structures, including the epiglottis, vocal cords and cartilage, can be injured during endotracheal intubation as the
endotracheal tube passes through the glottis. Injury to glottic structures may result in transient changes in voice, stridor
and laryngospasm. This is especially problematic in patients with di
Sore throat
A sore throat, dryness and pain on swallowing are common but transient symptoms following a general anaesthetic. They
occur due to in
Bronchospasm/laryngospasm
Bronchospasm and laryngospasm are more common in patients with hyper-responsive airways (e.g. asthma, recent
respiratory tract infection). It can also occur following aspiration of gastric contents during anaesthesia. Patients may
present with hypoxia, increased CO2 and reduced ventilation.
Bronchospasm causes a classical wheeze, whereas laryngospasm is associated with high-pitched stridor.
Aspiration of gastric contents
Aspiration of gastric contents is a rare but life-threatening complication. It typically occurs in non-fasted patients with
increased intra-abdominal pressure, impaired lower oesophageal sphincter competence or obtunded airway re
Pregnant patients, obese individuals, patients with hiatus hernias, patients with impaired laryngeal re
with reduced GCS are at increased risk of aspiration.
Clinical features include bronchospasm, laryngospasm, hypoxia, increased airway pressures. Furthermore, this may
collapse a lung lobe secondary to bronchial obstruction. Aspiration of gastric contents may result in pneumonia.
Injury to the trachea, bronchial structures or alveoli
This may present with subcutaneous emphysema or pneumothorax following an episode of anaesthesia. These are rare
complications associated with additional airway instrumentation or complex ventilation procedures (e.g. Bougie-assisted
intubations and one-lung ventilation).
Pneumothorax may also result from the rupture of pre-existing bullae.
Pulmonary oedema
Pulmonary oedema may occur in patients following laryngospasm or airway obstruction, especially during the recovery
phase from anaesthesia. Inspiratory e
resulting in pulmonary oedema.
Pulmonary oedema should be suspected in hypoxic patients following laryngospasm. On examination, there may be
audible
the Geeky Medics guide to the acute management of pulmonary oedema.
Pharyngeal obstruction
Pharyngeal obstruction is common due to sedation following anaesthesia, especially when using long-acting sedative
agents. This may be worsened by obstructive sleep apnoea (OSA). Pharyngeal obstruction can be identi
Initial management includes basic airway manoeuvres or placing the patient in the lateral position. When the cause is
more deeply seated (such as in OSA), overnight CPAP may be required following a general anaesthetic.
Hypoxia
Hypoxia is common among patients immediately following GA and is multifactorial. Hypoventilation secondary to
anaesthetic agents and opioid analgesia, along with atelectasis, leads to hypoxia. This may not be apparent as most
patients receive supplemental oxygen.
Patients with pre-existing respiratory disease, obese individuals and patients following upper abdominal or thoracic
surgeries are more prone to hypoxia.
Pulmonary embolismThough not a direct complication of anaesthesia, the conditions in the postoperative setting predispose to developing
venous thromboembolism. Reduced mobility following surgery and increased prothrombotic factors enhance thrombus
formation in deep veins. Patient-related factors such as dehydration and malignancy also contribute.
Identifying high-risk patients and using mechanical and pharmacological prophylaxis alongside general measures (e.g.
good hydration and early mobilisation) is important in reducing the risk of venous thromboembolism.

Cardiovascular complications

Hypotension
Hypotension following anaesthesia can occur for many reasons. Anaesthetic agents can reduce the contractility of the
heart and slow the heart rate. However, the e
hypotension should be considered.
Important causes include haemorrhage (resulting in hypovolaemia) and reduced vascular tone. Other causes (e.g.
myocardial infarction, pulmonary embolism and pneumothorax) should be excluded if hypotension persists despite initial
management.
Arrhythmias
Anaesthesia can cause both bradycardia and tachycardia. Post-operative pain is a common cause of sinus tachycardia
and should be managed appropriately. Other common causes include anxiety, electrolyte imbalances, cardiac surgery,
myocardial infarctions/ischaemia, hypoxia/hypercarbia, acid-base imbalances or worsening of pre-existing arrhythmias.
Management involves identifying and treating the cause of the arrhythmia and addressing any haemodynamic
compromise.
Hypertension
Hypertension is a common anaesthetic problem, especially in patients with poorly controlled essential hypertension. Other
causes include pain, anxiety, bladder distension,
the sympathetic nervous system producing hypertension.
Signi

Genitourinary system

Acute kidney injury (AKI)
Acute kidney injury (AKI) is a common complication in the postoperative period, which may present with a reduction in
urine output or worsening of metabolic parameters (e.g. acid-base balance and electrolyte imbalance). Causes are
broadly divided into pre-renal, intrinsic renal and post-renal.
Hypotension, hypovolaemia, nephrotoxic agents, sepsis or anaemia can contribute towards the development of AKI. Early
identi
and focusing on correcting precipitating factors is important. Some patients may require renal replacement therapy.
Urinary retention
Urinary retention is an infrequent complication of anaesthesia. Patients at risk include older patients and those with
prostatic hyperplasia. The ones who have received a spinal anaesthetic may be at higher risk.

Gastrointestinal complications

Post-operative nausea and vomiting (PONV)
PONV is a direct complication of anaesthetic agents and opioid analgesics. This is predictable, and high-risk patients
should be identi
Risk factors for PONV include\:Female sex
Non-smokers
Post-operative opioid use
Previous history of PONV
Type of surgery\: laparoscopic surgery, cholecystectomy and gynaecological surgery, middle ear surgeries, squint
corrections
General anaesthesia
Volatile anaesthesia
High-risk patients should be identi
avoid precipitants. Prophylactic antiemetic drugs are usually given. The type of antiemetics used depends on the risk
assessment and other patient factors.
Ileus
Post-operative ileus is a common complication of anaesthesia. Risk factors include type of surgery, use of opioids and
hypokalaemia. Reversible factors should be managed if identi
required.
Post-operative ileus commonly occurs following gastrointestinal surgery, open repair of abdominal aortic aneurysms, and
other surgical procedures where bowel handling may occur.

Neurological complications

Post-operative cognitive dysfunction
Postoperative cognitive dysfunction (POCD) is a decline in cognition apparent after a patient recovers from the acute
impact of surgery and hospital stay. This may present as acute delirium or be more subtle (e.g. memory impairment,
di
Risk factors for postoperative cognitive dysfunction include\:
Increasing age
Lower educational level
Cerebrovascular disease
POCD will become increasingly important as more older patients undergo surgical procedures. Patients and families
should be educated on POCD with an appropriate pre-operative assessment undertaken.
Peripheral nerve injuries (positioning-related)
Peripheral nerve injuries can occur due to prolonged durations in certain positions without appropriate preventive
strategies.
Table 1. Potential nerve injuries and strategies to prevent them.
Nerve/plexus Position Prevention
Brachial plexus Any
Avoid stretch or direct compression at the
neck/axilla
Avoid using shoulder braces to support the
Trendelenburg position.
Minimise shoulder abduction (aim \<90
degrees) and avoid external rotation.
Avoid rotation and
opposite side, try to keep head in neutral
position throughout.
Common
peroneal
Lithotomy
and lateral
decubitus
Pad lateral aspects of the upper
extreme lithotomy position and avoid lithotomy
position for more than 2 hoursRadial Any Avoid compression of the lateral humerus
Ulnar Any
Padding at the elbow, forearm supination, avoid
elbow extension and extreme
Other uncommon injuries include sciatic nerve injury in thin patients with prolonged supine positioning, common
peroneal nerve injury in the lithotomy position and radial nerve injury in the lateral position being compressed against the
humerus. It is important to identify and manage these injuries early.

Other complications

Hypothermia
Inadvertent perioperative hypothermia (IPH), de
general and regional anaesthesia.
Patient groups are at higher risk of developing hypothermia include\:
High ASA grade
Combined regional and general surgery
Emergency major surgery
Low BMI
Adverse e
drug metabolism and adverse cardiac events.
Prompt pre, intra and post-operative steps will prevent the development of IPH. Keeping patients warm during the pre-
operative phase, active warming during the intraoperative phase with
keeping the patient covered during the recovery are all important steps in preventing IPH.

Complications of regional anaesthesia

Diregional anaesthesia include central neuraxial blocks and peripheral nerve blocks.
Central neuraxial blocks (CNB) include
Subarachnoid block
Epidural blocks
Combined spinal epidural blocks
A subarachnoid block aims to place local anaesthetic in the subarachnoid space. In contrast, the local anaesthetic (LA) is
placed within the epidural space in an epidural block.
Di
anaesthesia/analgesia (e.g. brachial plexus, lumbar plexus or sciatic nerve block).
For more information, see the Geeky Medics guide to regional anaesthesia.
Post-dural puncture headache (PDPH)
A post-dural puncture headache (PDPH) occurs following an intentional dural puncture (with a spinal needle) or
unintentional dural puncture (with an epidural needle). The leak of CSF through the dural defect causes intracranial
hypotension leading to traction on intracranial structures.
Post-dural puncture headache usually occurs 72 hours after the dural puncture. It is usually a frontal or occipital headache
worsened by standing or sitting up and relieved by lying down. Patients should be referred to the anaesthetic team
whenever PDPH is suspected. It is important to exclude other causes of acute headache.
Management involves bed rest, adequate hydration, avoiding situations which would give rise to an increase in intracranial
pressure and simple analgesics. If the headache persists, an epidural blood patch can be performed.
Central neuraxial blocks (CNB)Though rare, potential major neurological complications following CNB include\:
1
Cord damage\: direct injury to the spinal cord or nerve roots caused by a needle or catheter, toxicity caused by local
anaesthetic agents
Cord ischaemia\: anterior spinal artery syndrome
Cord compression\: haematoma due to needle trauma, vascular anomaly, spinal tumour, coagulation
disorder/anticoagulants
Abscess\: exogenous infections via needle or haematogenous spread
Meningitis
Peripheral nerve injuries
Peripheral nerve/plexus injuries may occur in patients undergoing peripheral nerve blocks. These may manifest as sensory
or motor de

References

Miskovic, A., & Lumb, A. B. (2017). Postoperative pulmonary complications. B J A \: B r i t i s h J o u r n a l o f A n a e s t h e s i a , 1 1 8 (3), 317-
334.
Freedman, R., Herbert, L., O'Donnell, A., & Ross, N. (Eds.). (2022). O x f o r d H a n d b o o k o f A n a e s t h e s i a . Oxford University Press.
Webster, K. (2012). Peripheral nerve injuries and positioning for general anaesthesia. A n a e s t h e s i a T u t o r i a l o f t h e W e e k , 2 5 8 .
Riley С, A. J. Inadvertent perioperative hypothermia BJA Education, 2018. v. 18 (8). P . e 2 2 7-e 2 3 3 . d o i , 1 0 .
Mashour, G. A., Woodrum, D. T., & Avidan, M. S. (2015). Neurological complications of surgery and anaesthesia. B r i t i s h j o u r n a l
o f a n a e s t h e s i a , 1 1 4 (2), 194-203.
Cook, T. M., Counsell, D., & Wildsmith, J. A. W. (2009). Major complications of central neuraxial block\: report on the Third
National Audit Project of the Royal College of Anaesthetists. B r i t i s h j o u r n a l o f a n a e s t h e s i a , 1 0 2 (2), 179-190.

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Contents

Introduction
Respiratory system
Cardiovascular complications
Genitourinary systemSource\: geekymedics.com